Allergic Contact Dermatitis

Allergic contact dermatitis is a skin rash caused by exposure to a particular chemical or ingredient.

In some cases of allergic contact dermatitis, it is easy to figure out exactly what exposure caused a person’s rash. However, many cases of allergic contact dermatitis are not so obvious. We are exposed to a large number of chemicals and additives in our soaps, moisturizers, and other personal care products, and when allergic contact dermatitis is suspected, it can be challenging to figure out exactly which ingredient is the culprit. A poison ivy rash is the most famous example of allergic contact dermatitis. In poison ivy, exposure to urushiol causes a very itchy and uncomfortable skin rash exactly where the poison ivy leaves touch the skin. Oftentimes, an allergic contact dermatitis rash involves multiple areas of the body.

Your pediatric dermatologist works as a detective when suspecting allergic contact dermatitis and thinking about what agent could be the trigger.

Allergic contact dermatitis typically causes an itchy rash on your body. It may be localized to one area of the body (sometimes in the exact pattern of an exposure — e.g., a rectangle rash at the site of a bandage), or it may affect the skin diffusely. Allergic contact dermatitis typically looks like eczema — it can be pink and flaky, or it can cause small fluid-filled blisters. Allergic contact dermatitis is typically suspected based on the distribution of the rash on the body, or based on the timeline of how and when the rash occurred. It takes a few days after exposure to an offending agent for your allergic contact dermatitis to occur.

Allergic contact dermatitis is a skin reaction caused by repeated exposure to a particular chemical ingredient. Sometimes, an ingredient that you have tolerated well for many years will become an ingredient that you later develop sensitivity to in the form of allergic contact dermatitis. In immunologic terms, it is considered a type IV hypersensitivity reaction. Allergic contact dermatitis requires “sensitization,” or repeated exposure to a chemical. It is impossible to experience an allergic contact dermatitis rash the first time that your skin is exposed to a particular ingredient.

There are certain chemicals that are far more likely to cause allergic contact dermatitis than others. Sometimes, your pediatric dermatologist can correctly identify what is causing your allergic contact dermatitis based on your exposures and likelihood estimates. Other times, in-depth testing (patch testing) is recommended. 

Some of the most common causes of allergic contact dermatitis in children include the following:

• Nickel
• Poison ivy
• Fragrance
• Antibiotic ointments
• Lanolin
• Bandage adhesive
• Homemade slime

Allergic contact dermatitis is diagnosed clinically by your provider. This means that just by looking at your skin and listening to the history of your rash, your physician can diagnose allergic contact dermatitis. In most instances, we do not need to test the skin with a skin biopsy to confirm this rash.

To figure out what ingredient caused your allergic contact dermatitis, your physician works with you to determine the most likely trigger based on your history of exposures and based on the likelihood of ingredient allergies. In some cases, though, patch testing is recommended.

Patch testing helps your doctor figure out exactly what ingredient(s) your skin is most sensitive to. Patch testing is different than “prick testing,” the allergy testing most commonly performed by allergy doctors. Patch testing is typically performed by a dermatologist who has had special training in administering and interpreting the test, and it is not performed by all dermatology offices.

In patch testing, a small quantity of dozens of different ingredients will be taped to your back and body. Exactly which ingredients get patched to your body is determined by your patch testing doctor after they meet with you and learn about your history. Taped “patches” are left in place for several days and then removed.

Your provider has a specific guide that shows them exactly where each chemical was affixed to the skin, and can then suspect which ingredients you are most sensitive to by judging the amount of skin reaction that you have in each particular location. Patch testing does not hurt, but it does require multiple doctor’s visits during a weeklong period, and you will not be able to shower, bathe, or engage in very vigorous physical activities for a period of days so that the patches do not fall off.

The key form of treatment for allergic contact dermatitis is exposure avoidance. By avoiding contact with a known trigger, an uncomfortable allergic contact dermatitis rash can be avoided.

If an allergic contact dermatitis rash has already occurred, the most common treatment that we prescribe is a topical steroid. Topical steroids are very effective at reducing inflammation and itching in the affected skin. However, in some severe cases, oral steroids may be required. Occasionally, non-steroidal topical therapies can be pursued. Antihistamines may be prescribed to help with itching.

For patients with severe allergic contact dermatitis and for whom avoidance cannot be reasonably pursued, biologic therapy with dupilumab may be discussed. Dupilumab is FDA approved for moderate to severe atopic dermatitis (a distinct condition) in patients 6 months and older. Preliminary studies have demonstrated (off-label) improvement of symptoms for patients with allergic contact dermatitis treated with dupilumab.